U.S. patent number 10,029,563 [Application Number 14/667,813] was granted by the patent office on 2018-07-24 for one-way or selectable clutch with multiple rows of ratchet elements.
This patent grant is currently assigned to BorgWarner Inc.. The grantee listed for this patent is BORGWARNER, INC.. Invention is credited to James R. Papania.
United States Patent |
10,029,563 |
Papania |
July 24, 2018 |
One-way or selectable clutch with multiple rows of ratchet
elements
Abstract
A one-way or selectable clutch with multiple circumferential
rows of ratchet elements is disclosed. The clutch may include two
or more rows of ratchet elements extending between two or more
races. The device may be either a one-way clutch or a selectable
mechanical clutch, and afford the benefits of reduced backlash and
multiple modes of operation. Those modes may include
free-wheel/overrun in both clockwise and counterclockwise
directions, locked/transmit torque in both directions, locked in
clockwise and overrun in counterclockwise directions, and locked in
counterclockwise and overrun in clockwise directions.
Inventors: |
Papania; James R. (Bolingbrook,
IL) |
Applicant: |
Name |
City |
State |
Country |
Type |
BORGWARNER, INC. |
Auburn Hills |
MI |
US |
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Assignee: |
BorgWarner Inc. (Auburn Hills,
MI)
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Family
ID: |
54367452 |
Appl.
No.: |
14/667,813 |
Filed: |
March 25, 2015 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20150323020 A1 |
Nov 12, 2015 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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13124684 |
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PCT/US2009/060863 |
Oct 15, 2009 |
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61107571 |
Oct 22, 2008 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F16D
41/125 (20130101); B60K 17/344 (20130101); F16D
41/16 (20130101); F16D 41/14 (20130101); Y10T
74/19102 (20150115) |
Current International
Class: |
F16D
41/12 (20060101); F16D 41/16 (20060101); B60K
17/344 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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101240821 |
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Aug 2008 |
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CN |
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101285509 |
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Oct 2008 |
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CN |
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WO-03/067110 |
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Aug 2003 |
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WO |
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Other References
International Search Report and Written Opinion for related
international application No. PCT/US2009/060863; report dated May
27, 2010. cited by applicant .
International Preliminary Report on Patentability for related
international application No. PCT/US2009/060863; report dated Apr.
26, 2011. cited by applicant .
Office Action for related Chinese Application No. 200980139771.6;
action dated Aug. 22, 2016. cited by applicant.
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Primary Examiner: Boes; Terence
Attorney, Agent or Firm: Miller, Matthias & Hull LLP
Parent Case Text
RELATED APPLICATION
This application is a continuation-in-part of U.S. Ser. No.
13/124,684, filed on Apr. 18, 2011.
Claims
What is claimed is:
1. A clutch, comprising: a first race; a second race coaxially
positioned with respect to the first race; and a first plurality of
ratchet elements extending radially between the first and second
races, the first plurality of ratchet elements being mounted in the
first race; a first actuator cam ring having a plurality of axially
extending fingers for each of the first plurality of ratchet
elements, each of the plurality of axially extending fingers being
configured to shift circumferentially and engage a respective one
of the first plurality of ratchet elements to block engagement of
the respective ratchet element with the second race; wherein the
clutch further comprises a third race coaxially positioned with
respect to the first and second races, the second race being
positioned between the first race and the third race; wherein the
second race is a drive race configured to selectively drive the
first and third races; wherein the clutch further includes a second
plurality of ratchet elements mounted in the second race, the
second plurality of ratchet elements extending between the second
and third races; a second actuator cam ring having a second
plurality of axially extending fingers for each of the second
plurality of ratchet elements, each of the second plurality of
axially extending fingers being configured to shift
circumferentially and engage a respective one of the second
plurality of ratchet elements to block engagement of the respective
ratchet element with the third race; and wherein the first and
second actuator cam rings are moveable to select from among at
least four distinct operational modes of the clutch.
2. The clutch of claim 1, wherein some of the ratchet elements
extend in a clockwise direction, and some of the ratchet elements
extend in a counterclockwise direction.
3. The clutch of claim 1, wherein the ratchet elements include a
pivot axle from which extends a locking arm.
4. The clutch of claim 1, wherein the first race is machined to
have a plurality of mounting recesses into which each ratchet
element of the first plurality of ratchet elements is pivotably
mounted.
5. The clutch of claim 1, wherein the second race is machined to
have a plurality of mounting recesses into which each ratchet
element of the second plurality of ratchet elements is pivotably
mounted.
6. The clutch of claim 1, wherein each of the second and third
races are provided with a plurality of notches into which the
respective first and second pluralities of ratchet elements engage
and disengage.
7. The clutch of claim 1, wherein each of the second and third
races comprise a plurality of notches, each notch including a cam
surface and a shoulder, the cam surface being angled such that the
locking arm slides freely, and the shoulder engages the locking arm
to prevent further rotation.
8. The clutch of claim 1, wherein each ratchet element is
associated with a spring, the spring biasing the locking arm toward
one of the notches.
9. A method of operating a single clutch with reduced backlash and
bi-directional capacity, comprising: providing a clutch including
first, second, and third races, each coaxially positioned with
respect to the other races, a first plurality of ratchet elements
extending radially between the first and second races, the first
plurality of ratchet elements being mounted in the first race, the
second race being positioned between the first race and the third
race; forming the second race as a drive race to selectively drive
the first and third races; forming the clutch to have a second
plurality of ratchet elements mounted in the second race, with the
second plurality of ratchet elements extending between the second
race and the third race; providing first and second actuator cam
rings, each actuator cam ring having a plurality of axially
extending fingers for each of the respective first and second
pluralities of ratchet elements; rotating the respective actuator
cams in a first direction to cause each of the respective
associated pluralities of axially extending fingers to shift
circumferentially and engage a respective one of the first and
second pluralities of ratchet elements to block engagement of the
respective ratchet elements with the first and second races; and
rotating the respective actuator cams in a second direction to
cause each of the respective associated pluralities of axially
extending fingers to shift circumferentially and disengage a
respective one of the first and second pluralities of ratchet
elements to allow the respective ratchet elements to engage with
the first and second races.
10. The method of claim 9, further comprising multiple rows of
ratchet elements mounted in the same direction or opposite
directions.
11. The method of claim 9, wherein the rotating steps allow for
bi-directional use.
12. A motor vehicle transfer case, comprising: a housing formed by
a case and a cover, the case being operatively coupled to an output
of a transmission; an input shaft rotatably supported by an input
roller bearing and the case; a primary output shaft rotatably
supported by a rear output roller bearing in the cover; a secondary
output shaft rotatably supported at the lower portion of the
housing by a front output roller bearing, the secondary output
shaft having a bell-shaped flange operatively coupled to a bulge
joint to transmit torque; a drive sprocket splined to the primary
output shaft and operatively coupled to a lower driven sprocket,
the lower driven sprocket being rotatably supported by a rear
roller bearing to selectively transmit torque to the secondary
output shaft; and a selectable clutch axially situated between the
input shaft and the primary output shaft, the clutch unit
comprising a first race coupled to the primary output shaft, a
second race coupled to the input shaft and coaxially positioned
with respect to the first race, and a first plurality of ratchet
elements extending radially between the first and second races, the
first plurality of ratchet elements being mounted in the first
race; wherein the clutch unit further comprises a third race
coupled to the secondary output shaft and coaxially positioned with
respect to the first and second races, the second race being
positioned between the first race and the third race, the second
race being a drive race configured to selectively drive the first
and third races; and wherein the clutch unit further includes a
second plurality of ratchet elements mounted in the second race,
the second plurality of ratchet elements extending between the
second race and the third race, the first and second plurality of
ratchet elements being disposed circumferentially in multiple rows
between the first, second, and third races, and wherein each of the
ratchet elements includes a pivot axle from which extends a locking
arm, each of the first and second races being provided with a
plurality of notches into which the respective first and second
pluralities of ratchet elements engage and disengage.
13. The motor vehicle transfer case of claim 12, wherein some of
the ratchet elements of the clutch unit extend in a clockwise
direction and some of the ratchet elements extend in a
counterclockwise direction.
14. The motor vehicle transfer case of claim 12, wherein the clutch
allows for bi-directional use.
15. The motor vehicle transfer case of claim 12, wherein all of the
ratchet elements of the clutch unit extend in the same rotational
direction.
16. The motor vehicle transfer case of claim 12, wherein the first
and second circumferential rows of ratchet elements are radially
disposed with respect to the other.
17. The motor vehicle transfer case of claim 12, wherein the first
race is machined to have a plurality of mounting recesses into
which each ratchet element of the first plurality of ratchet
elements is pivotably mounted.
18. The motor vehicle transfer case of claim 12, wherein the second
race is machined to have a plurality of mounting recesses into
which each ratchet element of the second plurality of ratchet
elements is pivotably mounted.
19. The motor vehicle transfer case of claim 12, wherein each of
the plurality of notches include a cam surface and a shoulder, the
cam surface being angled such that the locking arm slides freely,
and the shoulder engages the locking arm to prevent rotation.
Description
FIELD OF THE DISCLOSURE
The present disclosure generally relates to clutch assemblies and,
more particularly, relates to radial ratchet one-way and
selectably-engageable clutches.
BACKGROUND OF THE DISCLOSURE
Transfer cases are often used in both full and part-time four-wheel
drive vehicles to distribute driving power received through an
input shaft from the vehicle transmission to a pair of output drive
shafts. One of the drive shafts powers the vehicle front wheels and
the other drive shaft powers the vehicle rear wheels. In vehicles
permitting shifting between two wheel drive and four wheel drive
modes, the input shaft of the transfer case provides continuous
power to one of its output shafts and selectively provides drive
power to the other output shaft by some type of disengageable or
otherwise adjustable coupling, such as a viscous coupling,
electro-magnetic clutch, or positionable spur gearing. Other drive
modes are sometimes provided, including four-wheel drive high for
higher four-wheel drive speeds, four-wheel drive low for lower
driving speeds, neutral for disengaging the transmission from the
front rear axles to allow towing, and locked four-wheel drive for
controlling wheel slippage.
Additionally, other transfer case applications have evolved, such
as on demand four-wheel drive, in which a transfer case, with its
related parts that provide four-wheel drive, is installed in the
vehicle, yet four-wheel drive mode is only engaged, by automatic
means, when there is a loss of two-wheel drive traction. Full time
or constant, four-wheel drive mode, sometimes referred to as
"all-wheel drive" is also currently available in some automotive
variants. In this mode, four-wheel drive is often not deselectable,
and thus remains a fixed configuration.
In the transfer cases used for these vehicles, certain elements, or
components, are required to transmit the driving force. More
particularly, certain elements are required to selectively transmit
the driving force during particular driving situations but not in
others. One example of a device used to selectively transmit
driving or rotational force, in a transfer case, is a one-way
clutch. One-way clutches are known devices having inner and outer
races with an engagement mechanism disposed therebetween. Generally
speaking, the engagement mechanism is designed to lock the races
together when the relative rotation of the races is in one
particular rotational direction. When the races rotate in the
opposite relative direction, the engagement mechanism is unlocked
and the races have free rotation relative to each other. In
application, when the races are fixed to concentric shafts, the
one-way clutch will function to hold the shafts together when
engaged, causing them to rotate in the same direction and thereby
transferring motive force, or drive torque, from one shaft to the
other. When the one-way clutch is disengaged, the shafts can then
free-wheel relative to each other.
Specific applications govern how the one-way clutch engagement is
designed. A one-way clutch may be designed to have one race as the
driving member and one as the driven member, or the clutch may be
designed to allow either shaft to act as the driving member during
different operating modes. In this manner, the locking mechanism of
the one-way clutch may be designed to engage in response to the
rotation of only one of the races, or the clutch may be designed so
as to engage if and/or as either race provides the proper relative
rotation.
The one-way clutch is typically used in circumstances in which
shaft to shaft, or shaft to race, rotational, torque-transferring
engagements are desirable, but a "hard" connection such as a spline
or keyed connection would not work. For example, during certain
operating parameters, a four-wheel drive vehicle experiences
driveline difficulties that arise from having the front and rear
wheels cooperatively driven, which can be alleviated by the use of
one-way clutch devices within the transfer case. When a four-wheel
drive vehicle turns a tight corner with four wheels coupled
together on a paved road, the vehicle may experience what is known
as "tight corner braking effect". This happens due to the inherent
physical geometry that affects objects rotating at different radial
distances from a center point. Two distinct effects generally occur
with four-wheel drive vehicles. First, when any vehicle enters a
curve the wheels on the outside of the curve must traverse a
greater circumferential distance than the wheels inside of the
curve due their greater radial distance from the center of the
curve. The tighter the curve, the greater difference in the rate of
rotational, angular speed between the inner wheels and the outer
wheels. Therefore, in a curve the outside wheels must rotate faster
than the inner wheels. This effect is exaggerated in a four-wheel
drive vehicle but is generally countered by the differential
assemblies of the vehicle installed at the front and rear axles.
Secondly, since the front wheels are also leading the vehicle
through the curve, they must rotate faster than the rear wheels.
With a solid four-wheel drive engagement there is no device (such
as a differential) to counter this action, and the slower moving
rear-wheels act in an undesirable braking manner.
To resolve this problem, one-way clutches have been employed in the
transfer case so as the vehicle begins turning a corner, the front
wheels (connected to transfer case output shaft through a one-way
clutch) are allowed to disengage and free-wheel faster than the
rear-wheels. Specifically, the driven shaft of the one-way clutch
(i.e. the output shaft to the four-wheel drive front wheels) begins
turning faster than the input or driving shaft, and the locking
mechanism of the one-way clutch disengages to allow free-wheeling
of the output shaft relative to the input shaft. This momentarily
takes the transfer case out of four-wheel drive mode, thus
preventing the "tight corner braking effect".
Another undesirable four-wheel drive driving effect occurs during
engine braking in a manual transmission of a four-wheel drive
vehicle when in four-wheel drive and coasting. The manual
transmission maintains a physical connection to the vehicle engine,
such that when the vehicle is allowed to coast, the engine places a
decelerating or braking force on the transfer case, both input and
output shafts, and ultimately on both front and rear wheels. The
normal and undesirable parasitic affect of engine braking through
the rear wheels of a manual transmission two-wheel drive vehicle
has a negative impact on fuel consumption and efficiency, which is
exacerbated in four-wheel drive vehicles by virtue of addition of
the front wheels. Thus, when a one-way clutch is used in a drive
line of the transfer case, the slowing of the input shaft through
the engine braking effect allows the output shaft (connected to the
front wheels) to disengage and freewheel, momentarily taking the
transfer case out of four-wheel drive and preventing the engine
braking effect from passing through the front wheels, reducing the
negative impact on fuel efficiency.
Finally, in an on-demand application, a one-way clutch can be
employed in the transfer case so that in a normal two-wheel drive
mode, if one of the rear wheels should slip during vehicle
acceleration, the rotating speed of the input shaft will increase,
so that the one-way clutch engaging elements will bring the
transfer case into four-wheel drive and the front wheels into a
driven mode.
While proving to be of great value, as transfer case design
technology utilizing one-way clutches has continued to evolve,
one-way clutch designs have revealed certain limitations. Most
importantly, while a one-way clutch could solve the above-motioned
problems and disadvantages, the one-way clutch could only work in
one direction, if used alone. In other words, the one-way
rotational forward engagement between the input and output shafts
in the transfer case could allow forward four-wheel drive movement,
but not reverse four-wheel drive movement. To provide this
functionality, additional mechanisms and devices are added to the
transfer case to supplement the limited functionality of one-way
clutches. However, this has added both weight and complexity
penalties to transfer case designs.
Concurrent ongoing design goals of reducing the mechanical
complexity and physical bulk of transfer cases while increasing
their functionally has brought about the design of another torque
transmitting device using the one-way clutch mechanism to allow
engagement in a bi-rotational, or two-way, manner. This device is
typically called a two-way clutch. A two-way clutch may solve all
the above four-wheel drive difficulties while providing full
forward and reverse functionality. It may allow the input shaft to
be designed as a driving member for four-wheel drive modes, in both
rotational directions while offering bi-directional free-wheel
movement of the driven output shaft as needed when the input shaft
is stationary or rotating slower than the output shaft.
Yet, even though conventional two-way clutch designs have been
useful in solving these and other four-wheel drive issues, it has
become apparent in applications that use a two-way clutch for a
four-wheel drive engagement that certain deficiencies still exist.
Specifically, there exists a physical angular distance from the
engaged inner connection between the races of the two-way clutch
for the first rotational direction to the engagement of the races
in the reverse, or second direction. This angular distance also
known as backlash, can cause mechanical problems as the two-way
clutch is repeatedly called on to change its driving rotational
direction over the service life of the transfer case. This is due
to the mechanical load brought to bear in the switch from one
rotational direct to the other. This rotational shift takes a form
of a high-impact shock loading that is not only absorbed by the
two-way clutch, but is also translated to the other components
attached to a two-way clutch in the drive line, all to a repetitive
detrimental effect. The shock loading is detrimental as it reduces
component life and reliability, while adding unpleasant ride
characteristics to the vehicle.
Some attempts have been made to reduce amount of backlash within
two-way clutch assemblies. These attempts have generally required
substantial, or radical, redesigns of transfer case structure. In
the typical two-way clutch, the structurally inherent backlash can
only be physically reduced to between about four and five degrees
of rotation. Even this seemingly small amount of backlash causes
the noted issues.
Therefore, there exists a need for improved clutch assemblies for
use in transfer cases having reduced or minimal backlash, which can
thereby reduce impact loading, extend clutch life, and improve
riding characteristics of vehicles.
SUMMARY OF THE DISCLOSURE
In accordance with one aspect of the disclosure, a clutch is
disclosed which comprises an inner race, an outer race, and a
plurality of ratchet elements extending between the inner and outer
races, the plurality of ratchet elements being disposed in axially
spaced multiple rows between the inner and outer races.
In accordance with another aspect of the disclosure, a method of
operating a clutch with reduced backlash and bi-directional
capacity is disclosed which comprises providing a clutch assembly
including of an inner race, an outer race, a locking arm, a cam
surface, and a shoulder, rotating the inner race clockwise relative
to the outer race, such rotation causing the locking arm to slide
along the cam surface thereby allowing inner race to move freely,
and rotating the inner race counterclockwise relative to the outer
race, such rotation causing the locking arm to engage the shoulder
and preventing further rotation.
In accordance with another aspect of the disclosure, a motor
vehicle transfer case is disclosed which comprises a housing formed
by a case and a cover, the case being operatively coupled to an
output of a transmission; an input shaft rotatably supported by an
input roller bearing and the case; a primary output shaft rotatably
supported by a rear output roller bearing in the cover; a secondary
output shaft rotatably supported at the lower portion of the
housing by a front output roller bearing, the secondary output
shaft having a bell-shaped flange operatively coupled to a bulge
joint to transmit torque; a drive sprocket splined to the primary
output shaft and operatively coupled to a lower driven sprocket the
lower driven sprocket being rotatably supported by a rear roller
bearing to selectively transmit torque to the secondary output
shaft; and a clutch assembly comprising of an inner race, an outer
race and a plurality of ratchet elements extending between the
inner and outer races, the plurality of ratchet elements being
disposed in axially spaced multiple rows between the inner and
outer races.
In accordance with yet another aspect of the disclosure, a further
embodiment of a motor vehicle transfer case is disclosed which
comprises three races, with two rows of radially spaced ratchets
between the respective races, and wherein the ratchets are
effective to provide four-mode functionality.
These and other aspects and features of the disclosure will become
more apparent upon reading the following detailed description in
view of the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view of a transfer case employing a
clutch manufactured in conjunction with the teachings of the
disclosure;
FIG. 2 is a fragmentary view of one embodiment of the clutch
assembly;
FIG. 3 is a cross-sectional view of the embodiment of FIG. 2, taken
along line 3-3 of FIG. 2;
FIG. 4 is a cross-sectional view of the embodiment of FIG. 2, taken
along line 4-4 of FIG. 2;
FIG. 5 is a cross-sectional view of another embodiment of the
present disclosure employing three races with two radially spaced
rows of ratchet elements all extending in the same direction;
FIG. 6 is a cross-sectional view of another embodiment of the
present disclosure, with two radially spaced rows of ratchet
elements, the ratchets of each row extending in opposite
directions;
FIG. 7 is a cross-sectional view of an embodiment of a modified
transfer case of FIG. 1;
FIGS. 8a through 8d depict various available modes of the transfer
case of FIG. 7, as would be viewed along lines 8-8 of FIG. 7;
and
While the present disclosure is susceptible to various
modifications and alternative embodiments, certain illustrative
embodiments thereof have been shown in the drawings and will be
described below in detail. It is to be understood, however, that
there is no disclosure to limit the present disclosure to the
specific forms disclosed, but on the contrary, the intention is to
cover all modifications, alternative constructions, and equivalents
falling within the spirit and scope of the present disclosure.
DETAILED DESCRIPTION OF THE DISCLOSURE
Referring now to the drawings and with specific reference to FIG.
1, a transfer case utilized in a four-wheel drive vehicle (not
shown) and incorporating the present disclosure is generally
referred to by reference numeral 10. The transfer case 10 includes
a housing 12 which is formed by a case 14 and a cover 16 which mate
along central line 18 in a conventional matter.
An input shaft 19, having an input end 20 and an output end 24 is
rotatably supported by an input roller bearing 22 and the case is
operatively coupled to an output of a transmission in a
conventional matter. Similarly, primary output shaft 24 is
rotatably supported by a rear output roller bearing 26 in the cover
16 in the conventional matter.
As will be noted in the drawings, the input and output shafts are
integral, but those of ordinary skill in the art will appreciate
that they may be in formed as two shafts splined together in a
conventional matter. Together the input and output shafts define
the main shaft of the transfer case.
In addition, the transfer case 10 of the present disclosure
includes a secondary output shaft 28 rotatably supported at the
lower portion of the housing 12 by a front output roller bearing
30. The secondary output shaft 28 has a bell-shape flange 32 which
is operatively coupled to a bulge joint (not shown) to transmit
torque to the front wheels (not shown) of the vehicle when it is in
a four-wheel drive mode.
A drive sprocket 34 is splined to the primary output shaft 24 and
rotates therewith in the upper portion of housing 12. The drive
sprocket 34 is operatively coupled to a lower driven sprocket 36 by
a chain 38 shown in phantom. The lower driven sprocket 36 is
rotatably supported in the lower portion of the housing 12 by rear
roller bearing 39 to selectively transmit torque to the secondary
output shaft 28. The one speed transfer case 10 described after
this point is conventional in the art.
However, with reference to the clutch of the present disclosure it
is generally referenced to by reference numeral 40. As shown best
in FIG. 2, in a first embodiment, the clutch 40 can include an
inner race 42, and outer race 44, and a plurality of ratchet
elements 46 extended between the inner and outer races 42 and 44.
The ratchet elements 46 may be provided in a first circumferential
row 46a, and an axially spaced second circumferential row 46b.
As will be understood by one of ordinary skill in the art, the
ratchet elements 46 may include a pivot axle 50 from which extends
a locking arm 52. The outer race 44 may be machined to have a
plurality of mounting recesses 54 into which each ratchet element
46 could be pivotably mounted. In other embodiments, the plurality
of ratchet elements 46 may be similarly mounted for pivotal motion
in the inner race 42.
Referring now to FIG. 3, the first row of ratchet elements 46a is
shown in more detail by way of cross-section. As shown, the pivot
axle 50 is mounted in the outer race 44 with the locking arm 52
extending toward the inner race 42 in a clockwise direction. In
turn, the inner race 42 is provided with a plurality of notches 56
into which the ratchet elements 46 can engage and disengage.
More specifically, each notch 56 includes a cam surface 58 and a
shoulder 60. The cam surface 58 is angled such that clockwise
rotation of the inner race 42 relative to the outer race 44 causes
the locking arm 52 to slide along the cam surface 58 thereby
allowing the inner race 42 to freely move. However, when the inner
race 42 tries to rotate in the counterclockwise direction relative
to the outer race 44, the locking arm 52 engages the shoulder 60
and prevents such rotation. A spring 62 is associated with each
ratchet element 46 to bias the locking arms 52 toward the notches
56.
Concurrent with the first row of ratchet elements 46a, however, is
the second row of ratchet elements 46b also mounted in the outer
race 44. As shown in FIG. 2, the second row 46b may be also
circumferentially supported within the outer race 44, but
laterally, i.e. axially, spaced from the first ratchet elements
46a. In addition, the second row of ratchet elements 46b may extend
circumferentially in the same clockwise direction as the first row
46a, or as shown in FIG. 4, may be mounted so as to extend in the
opposite, counterclockwise direction. If mounted in the same
direction, the resulting clutch assembly may have a significantly
reduced backlash as compared to conventional clutches, e.g., on the
order of a fifty percent reduction. Accordingly, the present
disclosure is referred to herein as having a reduced backlash
factor of, for example, 0.5. If mounted in opposite directions, the
resulting clutch assembly could operate in a bi-directional
capacity as will be appreciated by those skilled in the art.
In still further alternative embodiments, the first and second rows
of ratchet elements 46 may extend between more than two races. For
example, and referring now to FIG. 5, such a clutch may include
first, second, and third races 63, 64, 66, with a first row of
ratchet elements 46a extending between the first race 63 and the
second race 64, and a second row of ratchet elements 46b extending
between the second race 64 and the third race 66. As such, the
first and second rows of ratchet elements 46a and 46b are spaced
apart radially, rather than axially (FIG. 2). Referring now to FIG.
6, another embodiment of radially spaced first and second rows of
ratchet elements 46c and 46d are mounted to extend in opposite
directions rather than in the same direction, as the embodiment of
FIG. 5. Thus, the disclosure offers considerable flexibility, and
any give choice will depend on most useful or desired
geometry/configuration for a particular application. The latter
embodiments may provide four distinct modes of operation;
specifically: (1) freewheel/overrun of all three races in both
clockwise and counterclockwise directions; (2) locked/transmits
torque in both clockwise and counterclockwise directions; (3)
locked in clockwise direction and overruns in counterclockwise
direction; and (4) locked in counterclockwise direction and
overruns in clockwise direction, as described below.
An example of use of such radially spaced multiple rows of ratchet
elements 46 are as depicted in FIG. 7 and FIGS. 8A through 8D,
reflecting an alternate embodiment of the transfer case 10 of FIG.
1. Thus, FIG. 7 depicts a transfer case 10' that utilizes the
triple race configuration of FIG. 6; i.e., having mountings of the
ratchet elements 46c and 46d extending in opposed directions.
Thus, in comparison with the single or unitary shaft 19 of the
transfer case 10 of FIG. 1, the embodiment of FIG. 7 includes two
separate but coaxial shafts, rotatable about the axis a'-a'. Thus,
an engine input shaft 20' is supported via pocket bearings 25'
within a cupped end 27' of an output shaft 24'. In this embodiment,
the input shaft 20' incorporates the "driving" race 64 of FIG. 6,
while the rear output shaft 24' incorporates the race 66, coupled
with the rear wheels (not shown). As noted, the race 64 reflects
the input or "driving" race, and as such is configured to drive
either the rear wheels via race 66, the front wheels via race 63,
or to drive both front and rear wheels via engagement of both races
63 and 66, simultaneously. The ratchet elements 46c, situated
between the races 64 and 66, may thus be selectively controlled to
drive the rear wheels. On the other hand, the input shaft 20' may
also be selectively controlled to drive the front wheels through
the race 63 via operation of the row of ratchet elements 46d
situated between the races 63 and 64.
Continuing reference to FIG. 7, an actuator cam ring 70 is
configured to be selectively rotated through a small angle so as to
"clock" about the axis 18' between two limits to either block or to
free up the spring-loaded ratchet elements 46c via axially
extending fingers 72. For this purpose, the actuator cam ring 70
contains one integral finger 72 for each ratchet element 46c. A
separate actuator cam ring 74, also containing one finger 76 for
each ratchet element 46d, similarly works in cooperation with, but
independently of, the actuator cam ring 70 to either block or free
up the spring-loaded ratchet elements 46d, depending on a
particular desired driving mode; i.e. whether freewheeling, driving
only the rear wheels, driving only the front wheels, or driving
both front and rear wheels.
Referring now to FIGS. 8a through 8d, various operating modes are
depicted. FIG. 8a depicts a mode in which both front and rear
wheels are driven in a 4-wheel or all-wheel drive mode
configuration. In this embodiment, the race 64 is integral to the
input shaft 20' (see FIG. 7), and is situated centrally or between
the front and rear races 63 and 66. As such, the race 64 is
configured to drive races 63 and 64 in a counter clockwise
direction represented by arrow 80 (FIG. 8a). Thus, in the all-wheel
drive mode of FIG. 8a, the actuator cam rings 70 and 74 have both
been clocked to positions wherein each of their respective fingers
72, 76 are out of engagement with each of their respective sets of
ratchets 46c, 46d. As such, the springs 62 are free to urge the
ratchets into their respective notches 56, so as to cause
corresponding driving connections, i.e. in the direction of arrow
80, of each of the rear and front races 66 and 63.
Referring now to FIG. 8b, the actuator cam ring 70 has been rotated
clockwise to block the circumferential row or set of ratchets 46c,
while the actuator cam ring 74 remains at its position of FIG. 8a,
so that the ratchets 46d remain free to engage respective notches
56 in the race 66, as shown. Thus, in this mode only the rear
wheels are driven.
In FIG. 8c, the actuator cam ring 70 has been rotated to its open
finger position to free up the row of ratchets 46c, while the
actuator cam ring 74 has been rotated to a position in which its
fingers 76 block the row of ratchets 46d. In this position only the
front wheels can be driven by the input race 64.
Finally, in FIG. 8d, both actuator cam rings 70 and 74 have been
moved to positions in which the respective fingers 72 and 76 of
each cam ring are blocking all ratchets 46c and 46d. This
configuration represents a coasting or towing mode wherein all
races remain free, i.e. fully disconnected from the input for
"driving" race 64, regardless of the rotational direction of any
particular race with respect to another.
The variously described modes are not dispositive of all
capabilities of this disclosure. For example, those skilled in the
art will appreciate that the use of a reverse idler gear (not
shown) will provide vehicular reversing capabilities for the
described driving modes that are otherwise represented by FIGS. 8a
through 8c. Thus, with a reverse idler gear, the all-wheel drive
mode of FIG. 8a becomes a four-wheel or all-wheel reverse mode.
Similarly, FIGS. 8b and 8c may respectively become rear wheel-only
and front wheel-only reverse modes.
In the foregoing, it can therefore be seen that the disclosure can
be used to construct a clutch with greatly reduced backlash, e.g.
up to a fifty percent reduction. In addition, the orientation of
the races and plurality of ratchet elements can be used so as to
create a selectable clutch having at least having four modes of
operation.
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